Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus includes refrigerant circuits in which a high pressure shell compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected; a mixed refrigerant made up of a mixture of 1,1,2-trifluoroethylene, difluoromethane, and 2,3,3,3-tetrafluoropropene and configured to circulate through the refrigerant circuits, the mixed refrigerant containing less than 50 wt % of 1,2,2-trifluoroetylene and a mixing ratio of difluoromethane being between 0.7 times and two times (both inclusive) that of 1,2,2-trifluoroetylene in terms of weight ratio, in a state before the mixed refrigerant is enclosed in the refrigerant circuits; and a refrigerating machine oil enclosed in the refrigerant circuits and prepared such that difluoromethane is least soluble in the refrigerating machine oil.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application ofPCT/JP2014/077527 filed on Oct. 16, 2014, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus.

BACKGROUND ART

In recent years, there has been demand to reduce greenhouse gasses froma perspective of preventing global warming. Regarding refrigerants usedfor refrigeration cycle apparatus such as air-conditioning apparatus,those with a lower global warming potential (GWP) are being considered.The GWP of R410A widely used for air-conditioning apparatus at presentis as high as 2088. Difluoromethane (R32) that has begun to beintroduced recently has a considerably high GWP value of 675.

Examples of refrigerant with a low GWP include carbon dioxide (R744:GWP=1), ammonia (R717: GWP=0), propane (R290: GWP=6),2,3,3,3-tetrafluoropropenee (HFO-1234yf: GWP=4), and1,3,3,3-tetrafluoropropenee (HFO-1234ze: GWP=6).

These low-GWP refrigerants are difficult to apply to typicalair-conditioning apparatus because of the following problems.

-   -   R744: There is a problem in securing withstanding pressure        because of very high operating pressure. Also, because critical        temperature is as low as 31 degrees C., there is a problem of        how to secure performance in application to air-conditioning        apparatus.    -   R717: Because of high toxicity, there is a problem in ensuring        safety.    -   R290: Because of high flammability, there is a problem in        ensuring safety.    -   HFO-1234yf/HFO-1234ze: Because a volume flow rate increases at        low operating pressure, there is a problem of performance        deterioration due to increases in pressure loss.

A refrigerant capable of solving the above problems is1,1,2-trifluoroethylene (HFO-1123) (see, for example, Patent Literature1). The refrigerant has the following advantages, in particular.

-   -   Because of its high operating pressure and low volume flow rate,        the refrigerant involves a reduced pressure loss and can readily        ensure performance.    -   The refrigerant has a GWP of less than 1 and has an edge in        countermeasures against global warming.

CITATION LIST Patent Literature

Patent Literature 1: International Publication No. 2012/157764

Non-Patent Literature

Non-patent Literature 1: Andrew E. Feiring, Jon D. Hulburt,“Trifluoroethylene deflagration”, Chemical & Engineering News (22 Dec.1997) Vol. 75, No. 51, pp. 6

SUMMARY OF INVENTION Technical Problem

HFO-1123 has the following problem.

(1) An explosion occurs if ignition energy is applied underhigh-temperature, high-pressure conditions (see, for example, Non-patentLiterature 1).

To apply HFO-1123 to a refrigeration cycle apparatus, it is necessary tosolve the above problem.

Regarding the above problem, it has become clear that an explosion willoccur due to a chain of disproportionation reactions. This phenomenonwill occur under the following two conditions.

(1a) Ignition energy (hot portion) is produced in the refrigerationcycle apparatus (especially, a compressor), causing disproportionationreaction.

(1b) Under high-temperature, high-pressure conditions,disproportionation reaction spreads in chains.

The present invention is intended to obtain a refrigeration cycleapparatus capable of inhibiting disproportionation reaction that usesHFO-1123.

Solution to Problem

A refrigeration cycle apparatus according to one embodiment of thepresent invention includes a refrigerant circuit in which a highpressure shell compressor, a condenser, an expansion mechanism and anevaporator are connected; a mixed refrigerant circulating through therefrigerant circuit and containing 1,1,2-trifluoroethylene,difluoromethane and 2,3,3,3-tetrafluoropropene mixed with each other,wherein, in a state prior to introduction of the mixed refrigerant intothe refrigerant circuit, a mixing ratio of 1,2,2-trifluoroetylene isless than 50 wt % and a mixing ratio of difluoromethane is 0.7 times amixing ratio of 1,2,2-trifluoroetylene or larger, but not more than twotimes of the mixing ratio of 1,2,2-trifluoroetylene in terms of weightratio; and a refrigerating machine oil enclosed in the refrigerantcircuit and prepared such that the difluoromethane is least solubletherein, from among 1,1,2-trifluoroethylene, difluoromethane and2,3,3,3-tetrafluoropropene.

Advantageous Effects of Invention

By using the mixed refrigerant containing less than 50 wt % of1,1,2-trifluoroethylene in a state before the mixed refrigerant isenclosed in the refrigerant circuit, the refrigeration cycle apparatusaccording to one embodiment of the present invention keeps down anamount of 1,1,2-trifluoroethylene in the refrigerant circuit. This makesit possible to keep 1,1,2-trifluoroethylene from causingdisproportionation reaction.

Also, the refrigeration cycle apparatus according to the presentinvention uses a refrigerating machine oil prepared such thatdifluoromethane will be least soluble in the refrigerating machine oil.This can keep a proportion of 1,1,2-trifluoroethylene in the mixedrefrigerant from increasing even during operation of the refrigerationcycle apparatus. Thus, the refrigeration cycle apparatus according tothe present invention can keep 1,1,2-trifluoroethylene from causingdisproportionation reaction even during operation of the refrigerationcycle apparatus.

Also, in the mixed refrigerant used for the refrigeration cycleapparatus according to the present invention, the mixing ratio ofdifluoromethane is 0.7 times the mixing ratio of 1,2,2-trifluoroetyleneor more, but not more than two times the mixing ratio of1,2,2-trifluoroetylene in terms of weight ratio. Consequently,1,1,2-trifluoroethylene and difluoromethane can be brought into apseudo-azeotropic state. Thus, the refrigeration cycle apparatusaccording to the present invention can inhibit separation between1,1,2-trifluoroethylene and difluoromethane, and thereby further keep1,1,2-trifluoroethylene from causing disproportionation reaction.

Also, to reduce a proportion of 1,1,2-trifluoroethylene in the mixedrefrigerant, the refrigeration cycle apparatus according to the presentinvention mixes not only difluoromethane, but also2,3,3,3-tetrafluoropropenee. Thus, the present invention can reduce theGWP of mixed refrigerant as well.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram of a refrigeration cycle apparatus 10according to an embodiment of the present invention (during cooling).

FIG. 2 is a circuit diagram of the refrigeration cycle apparatus 10according to the embodiment of the present invention (during heating).

FIG. 3 is a longitudinal sectional view of a compressor 12 according tothe embodiment of the present invention.

FIG. 4 is a diagram showing amounts of refrigerants dissolved inrefrigerating machine oil 60 according to the embodiment of the presentinvention.

FIG. 5 is a diagram showing amounts of refrigerants dissolved in therefrigerating machine oil 60 according to the embodiment of the presentinvention.

FIG. 6 is a diagram showing a composition ratio of HFO-1234yf whenrefrigerants making up a mixed refrigerant are dissolved in therefrigerating machine oil 60 at ratios shown in FIGS. 4 and 5.

DESCRIPTION OF EMBODIMENTS

Embodiment

FIGS. 1 and 2 are circuit diagrams of a refrigeration cycle apparatus 10according to an embodiment of the present invention, where FIG. 1 showsa refrigerant circuit 11 a during cooling and FIG. 2 shows a refrigerantcircuit 11 b during heating.

According to the present embodiment, the refrigeration cycle apparatus10 is an air-conditioning apparatus. Note that the present embodiment isalso applicable when the refrigeration cycle apparatus 10 is other thanan air-conditioning apparatus (e.g., a heat pump cycle apparatus).

In FIGS. 1 and 2, the refrigeration cycle apparatus 10 includesrefrigerant circuits 11 a and 11 b through which refrigerant circulates.

The refrigerant circuits 11 a and 11 b are connected with a compressor12 which is a high pressure shell compressor (compressor adapted todischarge the refrigerant compressed by a compression element into anairtight container), a four-way valve 13, an outdoor heat exchanger 14,an expansion valve 15, and an indoor heat exchanger 16. The compressor12 compresses the refrigerant. The four-way valve 13 changes a flowdirection of the refrigerant between cooling mode and heating mode. Theoutdoor heat exchanger 14 operates as a condenser during cooling andcauses the refrigerant compressed by the compressor 12 to reject heat.The outdoor heat exchanger 14 operates as an evaporator during heating,and exchanges heat between outdoor air and the refrigerant expanded bythe expansion valve 15 and thereby heats the refrigerant. The expansionvalve 15 is an example of an expansion mechanism. The expansion valve 15expands the refrigerant caused to reject heat by the condenser. Theindoor heat exchanger 16 operates as a condenser during heating, andmakes the refrigerant compressed by the compressor 12 to reject heat.The indoor heat exchanger 16 operates as an evaporator during cooling,and exchanges heat between indoor air and the refrigerant expanded bythe expansion valve 15 and thereby heats the refrigerant. Note that whenthe refrigeration cycle apparatus 10 does only one of cooling andheating, the four-way valve 13 is not necessary.

The refrigeration cycle apparatus 10 further includes a controller 17.

The controller 17 is, for example, a microcomputer. Although only aconnection between the controller 17 and compressor 12 is shown in FIGS.1 and 2, the controller 17 is connected not only to the compressor 12,but also to various elements connected to the refrigerant circuits 11 aand 11 b. The controller 17 monitors states of the elements and controlsthe elements.

In the present embodiment, mixed refrigerant made up of a mixture of1,1,2-trifluoroethylene (HFO-1123), difluoromethane (R32), and2,3,3,3-tetrafluoropropenee (HFO-1234yf) is used as the refrigerantcirculating through the refrigerant circuits 11 a and 11 b (in otherwords, the refrigerant enclosed in the refrigerant circuits 11 a and 11b). In a state before the mixed refrigerant is enclosed in therefrigerant circuits 11 a and 11 b, the mixed refrigerant contains lessthan 50 wt % of HFO-1123 and a mixing ratio of R32 is between 0.7 timesand two times (both inclusive) that of HFO-1123 in terms of weightratio. As the mixing ratio of R32 is set between 0.7 times and two times(both inclusive) that of HFO-1123 in terms of weight ratio, the R32 andHFO-1123 are brought into a pseudo-azeotropic state (becomepseudo-azeotropic refrigerants).

Also, in the refrigeration cycle apparatus 10 according to the presentembodiment, refrigerating machine oil 60 is enclosed in the refrigerantcircuits 11 a and 11 b. Most of the refrigerating machine oil 60 isaccumulated at a bottom of an airtight container of the compressor 12 asdescribed later. The refrigerating machine oil 60 has been prepared suchthat R32 will be least soluble of HFO-1123, R32, and HFO-1234yf therein.Furthermore, according to the present embodiment, the refrigeratingmachine oil 60 has been prepared such that HFO-1234yf will be moresoluble therein than HFO-1123.

The refrigerating machine oil 60 used in the present embodiment, may be,for example, polyol ester. Polyol ester is a product of esterificationof a fatty acid and polyhydric alcohol (polyol). Solubility (ease ofdissolution) of the refrigerant in polyol ester can be prepared byadjusting a carbon number of the fatty acid, a molecular structure ofthe fatty acid (whether to use a branched-chain fatty acid or anunbranched (straight-chain) fatty acid), a carbon number of thepolyhydric alcohol, and a molecular structure of the polyhydric alcohol(whether to use a branched-chain polyhydric alcohol or an unbranched(straight-chain) polyhydric alcohol).

Note that the refrigerating machine oil 60 used in the presentembodiment is not limited to polyol ester, and polyvinyl ether orpolyalkylene glycol may be used alternatively. Polyvinyl ether is acompound in which alkyl groups are linked to side chains of astraight-chain hydrocarbon via ether linkages. By varying components ofthe alkyl group linked to the side chains via ether linkages, thesolubility (ease of dissolution) of the refrigerant in polyvinyl ethercan be adjusted. Polyalkylene glycol is a compound in which a propyleneoxide and ethylene oxide are linked together in chains via etherlinkages. By varying a ratio between the propylene oxide and ethyleneoxide the solubility (ease of dissolution) of the refrigerant inpolyalkylene glycol can be adjusted.

Of course, the refrigerating machine oil 60 may be prepared by mixing atleast two of polyol ester, polyvinyl ether, and polyalkylene glycol.

Also, regarding amounts of the mixed refrigerant and refrigeratingmachine oil 60 before enclosure in the refrigerant circuits 11 a and 11b, the mixed refrigerant is set between one and four times (bothinclusive) the refrigerating machine oil 60 in terms of weight ratio.

FIG. 3 is a longitudinal sectional view of the compressor 12 accordingto the embodiment of the present invention. Note that hatching used toindicate a section is omitted in FIG. 3.

According to the present embodiment, the compressor 12, which is a highpressure shell compressor (compressor adapted to discharge therefrigerant compressed by a compression element 30 into an airtightcontainer 20), is a single-cylinder rotary compressor. Note that thepresent embodiment is also applicable even if the compressor 12 is amulti-cylinder rotary compressor or scroll compressor.

In FIG. 3, the compressor 12 includes an airtight container 20, acompression element 30, an electrically-operated element 40, and a shaft50.

The airtight container 20 is an example of a container. The airtightcontainer 20 is equipped with a suction pipe 21 adapted to suck therefrigerant and a discharge pipe 22 adapted to discharge therefrigerant.

The compression element 30 is housed in airtight container 20.Specifically, the compression element 30 is installed in lower innerpart of the airtight container 20. The compression element 30 compressesthe refrigerant sucked by the suction pipe 21.

The electrically-operated element 40 is also housed in airtightcontainer 20. Specifically, the electrically-operated element 40 isinstalled at that position in the airtight container 20 through whichthe refrigerant compressed by the compression element 30 passes beforebeing discharged from the discharge pipe 22. That is, theelectrically-operated element 40 is installed inside the airtightcontainer 20 and above the compression element 30. Theelectrically-operated element 40 drives the compression element 30. Theelectrically-operated element 40 is a concentrated winding motor.

The refrigerating machine oil 60 configured to lubricate a slidingportion of the compression element 30 is accumulated at a bottom of theairtight container 20.

Details of the compression element 30 will be described below.

The compression element 30 includes a cylinder 31, a rolling piston 32,a vane (not shown), a main bearing 33, and a secondary bearing 34.

An outer circumference of the cylinder 31 is substantially circular inshape in planar view. A cylinder chamber, which is a space substantiallycircular in shape in planar view, is formed inside the cylinder 31. Thecylinder 31 is open at opposite ends in an axial direction.

The cylinder 31 is provided with a vane groove (not shown) that extendsradially, being communicated with the cylinder chamber. A back pressurechamber, which is a space shaped substantially circular in planar viewand communicated with the vane groove is formed on an outer side of thevane groove.

The cylinder 31 is provided with a suction port (not shown) throughwhich a gas refrigerant is sucked from the refrigerant circuits 11 a and11 b. The suction port penetrates into the cylinder chamber from anouter circumferential surface of the cylinder 31.

The cylinder 31 is provided with a discharge port (not shown) throughwhich compressed refrigerant is discharged from the cylinder chamber.The discharge port is formed by cutting out an upper end face of thecylinder 31.

The rolling piston 32 is ring-shaped. The rolling piston 32 performseccentric motion in the cylinder chamber. The rolling piston 32 slidablyfits over an eccentric shaft portion 51 of the shaft 50.

The vane is shaped as a flat substantially rectangular parallelepiped.The vane is installed in the vane groove of the cylinder 31. The vane isconstantly pressed against the rolling piston 32 by a vane springprovided in the back pressure chamber. Because high pressure ismaintained in the airtight container 20, when the compressor 12 startsoperating, a force caused by a difference between pressure in theairtight container 20 and pressure in the cylinder chamber acts on aback surface (i.e., a surface facing the back pressure chamber) of thevane. Therefore, the vane spring is used to press the vane against therolling piston 32 mainly during startup of the compressor 12 (when thereis no difference between the pressures in the airtight container 20 andcylinder chamber).

The main bearing 33 is substantially inverse T-shaped when viewed from aside. The main bearing 33 slidably fits over a main shaft portion 52,which is that part of the shaft 50 that is located above the eccentricshaft portion 51. The main bearing 33 blocks upper part of the cylinderchamber and the vane groove of the cylinder 31.

The secondary bearing 34 is substantially T-shaped as viewed from aside. The secondary bearing 34 slidably fits over a secondary shaftportion 53, which is that part of the shaft 50 that is located below theeccentric shaft portion 51. The secondary bearing 34 blocks lower partof the cylinder chamber and the vane groove of the cylinder 31.

The main bearing 33 includes a discharge valve (not shown). A dischargemuffler 35 is attached to an outer side of the main bearing 33.High-temperature, high pressure gas refrigerant discharged through thedischarge valve enters the discharge muffler 35 once and then getsreleased into a space in the airtight container 20 from the dischargemuffler 35. Note that the discharge valve and discharge muffler 35 maybe provided on the secondary bearing 34 or on both main bearing 33 andsecondary bearing 34.

Material of the cylinder 31, main bearing 33, and secondary bearing 34is gray iron, sintered steel, carbon steel, or other steel. Material ofthe rolling piston 32 is alloy steel containing, for example, chromiumor other metal. Material of the vane is, for example, high-speed toolsteel.

A suction muffler 23 is provided on a side of the airtight container 20.The suction muffler 23 sucks low-pressure gas refrigerant from therefrigerant circuits 11 a and 11 b. When liquid refrigerant returns, thesuction muffler 23 keeps the liquid refrigerant from getting directlyinto the cylinder chamber of the cylinder 31. The suction muffler 23 isconnected to the suction port of the cylinder 31 through the suctionpipe 21. A main body of the suction muffler 23 is fixed to a side faceof the airtight container 20 by welding or another method.

Details of the electrically-operated element 40 will be described below.

According to the present embodiment, the electrically-operated element40 is a brushless DC (Direct Current) motor. Note that the presentembodiment is also applicable even if the electrically-operated element40 is a motor (e.g., an induction motor) other than a brushless DCmotor.

The electrically-operated element 40 includes a stator 41 and a rotor42.

The stator 41 is fixed in abutment with an inner circumferential surfaceof the airtight container 20. The rotor 42 is installed inside thestator 41 with a gap about 0.3 to 1 mm in size provided therebetween.

The stator 41 includes a stator core 43 and a stator winding 44. Thestator core 43 is produced by punching plural flat rolled magnetic steelsheets 0.1 to 1.5 mm in thickness into a predetermined shape, laminatingthe steel sheets in an axial direction, and fixing the steel sheets bycalking, welding, or another method. The stator winding 44 is woundaround the stator core 43 by concentrated winding via an insulatingmember 48. Material of the insulating member 48 is, for example, PET(polyethylene terephthalate), PBT (polybutylene terephthalate), FEP(tetrafluoroethylene hexafluoropropylene copolymer), PFA(tetrafluoroethylene perfluoroalkylvinylether copolymer), PTFE(polytetrafluoroethylene), LOP (liquid crystal polymer), PPS(polyphenylene sulfide), or phenol resin. The stator winding 44 isconnected with lead wires 45.

Plural notches are formed at substantially equal intervals in acircumferential direction on an outer circumference of the stator core43. Each of the notches serves as a passage for the gas refrigerantreleased from the discharge muffler 35 into the space in the airtightcontainer 20. Each of the notches also serves as a passage for therefrigerating machine oil 60 returning to the bottom of the airtightcontainer 20 from a top of the electrically-operated element 40.

The rotor 42 includes a rotor core 46 and permanent magnets (not shown).As with the stator core 43, the rotor core 46 is produced by punchingplural flat rolled magnetic steel sheets 0.1 to 1.5 mm in thickness intoa predetermined shape, laminating the steel sheets in an axialdirection, and fixing the steel sheets by calking, welding, or anothermethod. The permanent magnets are inserted into plural insertion holesformed in the rotor core 46. For example, ferrite magnets or rare earthmagnets are used as the permanent magnets.

Plural through-holes are formed, penetrating the rotor core 46substantially in the axial direction. As with the notches in the statorcore 43, each of the through-holes serves as a passage for the gasrefrigerant released from the discharge muffler 35 into the space in theairtight container 20.

A power supply terminal 24 (e.g., a glass terminal) for use to connectto an external power supply is attached to a top of the airtightcontainer 20. The power supply terminal 24 is fixed to the airtightcontainer 20, for example, by welding. The lead wires 45 from theelectrically-operated element 40 are connected to the power supplyterminal 24.

The discharge pipe 22 with opposite ends in the axial direction open isattached to the top of the airtight container 20. The gas refrigerantdischarged from the compression element 30 is discharged from the spacein the airtight container 20 to the refrigerant circuits 11 a and 11 boutside through the discharge pipe 22.

Operation of the compressor 12 will be described below.

Electric power is supplied from the power supply terminal 24 to thestator 41 of the electrically-operated element 40 via the lead wires 45.Consequently, the rotor 42 of the electrically-operated element 40rotates. As the rotor 42 rotates, the shaft 50 fixed to the rotor 42rotates. Along with rotation of the shaft 50, the rolling piston 32 ofthe compression element 30 rotates eccentrically in the cylinder chamberof the cylinder 31 of the compression element 30. Space between thecylinder 31 and rolling piston 32 is divided into two by the vane of thecompression element 30. Volumes of the two spaces change with rotationof the shaft 50. One of the spaces increases in volume gradually,thereby sucking the refrigerant from the suction muffler 23. The otherspace decreases in volume gradually, thereby compressing the gasrefrigerant in the space. The compressed gas refrigerant is dischargedonce into the space in the airtight container 20 through the dischargemuffler 35. The discharged gas refrigerant passes through theelectrically-operated element 40 and gets discharged out of the airtightcontainer 20 through the discharge pipe 22 on top of the airtightcontainer 20.

The refrigeration cycle apparatus 10 uses the high pressure shellcompressor 12. That is, the refrigeration cycle apparatus 10 uses thecompressor 12 in which temperature inside the airtight container 20 iselevated. Also, the refrigeration cycle apparatus 10 uses HFO-1123 asthe refrigerant. Consequently, HFO-1123 can cause disproportionationreaction, raising concerns that a chain of disproportionation reactionsmight result in an explosion.

However, the refrigeration cycle apparatus 10 according to the presentembodiment keeps down an amount of HFO-1123 in the refrigerant circuits11 a and 11 b by using mixed refrigerant that contains less than 50 wt %of HFO-1123 in a state before the mixed refrigerant is enclosed in therefrigerant circuits 11 a and 11 b. The refrigeration cycle apparatus 10can keep HFO-1123 from causing disproportionate reaction. Also, therefrigeration cycle apparatus 10 uses the refrigerating machine oil 60prepared such that R32 will be least soluble therein. Consequently, aproportion of HFO-1123 in the mixed refrigerant can be kept fromincreasing even during operation of the refrigeration cycle apparatus10. Therefore, the refrigeration cycle apparatus 10 according to thepresent embodiment can keep HFO-1123 from causing disproportionatereaction even during operation of the refrigeration cycle apparatus 10.Furthermore, in the mixed refrigerant used for the refrigeration cycleapparatus 10 according to the present invention a mixing ratio of R32 isset between 0.7 times and two times (both inclusive) that of HFO-1123 interms of weight ratio. Consequently, R32 and HFO-1123 can be broughtinto a pseudo-azeotropic state. Thus, the refrigeration cycle apparatus10 according to the present embodiment, can inhibit separation betweenR32 and HFO-1123, and thereby further inhibit disproportionationreaction of HFO-1123. That is, the refrigeration cycle apparatus 10according to the present embodiment can prevent explosions caused by achain of disproportionation reactions of HFO-1123 and ensure high safetyeven when HFO-1123 is used.

Note that when the effect of reducing global warming potential (GWP) byuse of HFO-1123 is considered, preferably the ratio of HFO-1123 in themixed refrigerant is 10 wt % or above.

Also, to reduce the proportion of HFO-1123 in the mixed refrigerant therefrigeration cycle apparatus 10 according to the present embodiment,mixes not only R32, but also HFO-1234yf. This makes it possible toreduce the GWP of the mixed refrigerant as well.

Now, an example of a composition ratio of mixed refrigerant and anexample of an amount of refrigerant dissolved in the refrigeratingmachine oil 60 will be introduced.

FIGS. 4 and 5 are diagrams showing amounts of refrigerants dissolved inthe refrigerating machine oil 60 according to the embodiment of thepresent invention, where FIG. 4 shows dissolved amounts of refrigerantsduring normal operation while FIG. 5 shows dissolved amounts ofrefrigerants during overload operation. Also, in FIGS. 4 and 5, in astate before the mixed refrigerant is enclosed in the refrigerantcircuits, composition of the mixed refrigerant is as follows in terms ofweight ratio: HFO-1123:R32:HFO-1234yf=40:40:20. Note that the ordinateshown in FIGS. 4 and 5 represents the amounts of soluble HFO-1123 andR32 per 100 parts by weight of the refrigerating machine oil 60.

As shown in FIGS. 4 and 5, the amounts of refrigerants (the refrigerantsmaking up the mixed refrigerant) dissolved in the refrigerating machineoil 60 satisfy the following relationship: HFO-1234yf >HFO-1123>R32.When attention is focused on conditions in which temperature of therefrigerating machine oil 60 during normal operation is 60 degrees C.(position of the broken line in FIG. 4), if the refrigeration cycleapparatus 10 is operating under these conditions, dew point temperatureof the mixed refrigerant is 40 degrees C. and temperature of therefrigerating machine oil 60 accumulated in the compressor 12 is 60degrees C. (in other words, a degree of superheat of discharge from thecompressor 12 is 20 degrees C.). Under these operating conditions, thedissolved amount of HFO-1234yf is 38 parts by weight (point A) and thedissolved amount of HFO-1123 is 33 parts by weight (point B). Also, thedissolved amount of R32 is 17 parts by weight, which is 21 parts lessthan the dissolved amount of HFO-1234yf.

That is, by adjusting the amounts of refrigerants (the refrigerantsmaking up the mixed refrigerant) dissolved in the refrigerating machineoil 60 in such a way as to satisfy the relationship ofHFO-1234yf>HFO-1123>R32, it is possible to reduce the proportion ofHFO-1234yf in the mixed refrigerant circulating in the refrigerantcircuits 11 a and 11 b. This increases pressure of the mixed refrigerantand thereby decreases a temperature glide of the mixed refrigerant in acondensation process and an evaporation process, making it possible toimprove performance (COP) of the refrigeration cycle apparatus 10.

Also, if the amounts of refrigerants (the refrigerants making up themixed refrigerant) dissolved in the refrigerating machine oil 60 isprepared so as to satisfy the relationship of HFO-1234yf>HFO-1123>R32,during operation of the refrigeration cycle apparatus 10, the proportionof HFO-1234yf in the mixed refrigerant circulating in the refrigerantcircuits 11 a and 11 b does not exceed the proportion at the time ofenclosure of the mixed refrigerant in the refrigerant circuits 11 a and11 b. Thus, the performance of refrigeration cycle apparatus 10 does notdegrade.

On the other hand, when attention is focused on conditions in whichtemperature of the refrigerating machine oil 60 during overloadoperation is 60 degrees C. (position of the broken line in FIG. 5), ifthe refrigeration cycle apparatus 10 is operating under theseconditions, the dew point temperature of the mixed refrigerant is 60degrees C. and the temperature of the refrigerating machine oil 60accumulated in the compressor 12 is 100 degrees C. (in other words, thedegree of superheat of discharge from the compressor 12 is 40 degreesC.). Under these operating conditions, the dissolved amount ofHFO-1234yf is 26 parts by weight (point D) and the dissolved amount ofHFO-1123 is 22 parts by weight (point E). Also, the dissolved amount ofR32 is 7 parts by weight, which is 19 parts by weight less than thedissolved amount of HFO-1234yf.

The higher the refrigerant temperature, the less soluble the refrigerantis in the refrigerating machine oil 60. That is, during overloadoperation in which the refrigerant temperature is higher than duringnormal operation, the amount of refrigerant dissolved in therefrigerating machine oil 60 is smaller than during normal operation.Consequently, the proportion of HFO-1234yf in the mixed refrigerantcirculating in the refrigerant circuits 11 a and 11 b during overloadoperation is higher than during normal operation. Because HFO-1234yfinvolves a low operating pressure, by adjusting the amounts ofrefrigerants (the refrigerants making up the mixed refrigerant)dissolved in the refrigerating machine oil 60 so as to satisfy therelationship of HFO-1234yf>HFO-1123>R32, it is also possible to achievethe effect of reducing refrigerant pressure on a high-pressure sideduring overload operation.

FIG. 6 is a diagram showing a composition ratio of HFO-1234yf whenrefrigerants making up a mixed refrigerant are dissolved in therefrigerating machine oil 60 at ratios shown in FIGS. 4 and 5. Theabscissa in FIG. 6 represents the weight ratio of the mixed refrigerantand refrigerating machine oil 60 before the mixed refrigerant isenclosed in the refrigerant circuits 11 a and 11 b (weight of the mixedrefrigerant/weight of the refrigerating machine oil 60). Also, theordinate in FIG. 6 represents the proportion of HFO-1234yf in the mixedrefrigerant circulating in the refrigerant circuits 11 a and 11 b. Notethat curve Y represents the composition ratio of HFO-124yf during normaloperation while curve Z represents the composition ratio of HFO-1234yfduring overload operation.

When the mixed refrigerant and refrigerating machine oil 60 are enclosedin the refrigerant circuits 11 a and 11 b such that a weight ratio ofthe mixed refrigerant will be equal to or less than the refrigeratingmachine oil 60, the ratio of the mixed refrigerant to the refrigeratingmachine oil 60 is so low that an amount of change in the composition ofthe mixed refrigerant becomes too large, which makes the composition ofthe mixed refrigerant unstable and thereby makes it difficult to controlthe refrigeration cycle apparatus 10. On the other hand, if the mixedrefrigerant and refrigerating machine oil 60 are enclosed in therefrigerant circuits 11 a and 11 b such that the weight ratio of themixed refrigerant will be four times or more the refrigerating machineoil 60, the ratio of the mixed refrigerant to the refrigerating machineoil 60 is so high that an amount of change in HFO-1234yf becomes assmall as 0.5 wt %. This decreases the COP improvement effect andhigh-pressure reduction effect described above. According to the presentembodiment, since the mixed refrigerant and refrigerating machine oil 60are enclosed in the refrigerant circuits 11 a and 11 b such that themixed refrigerant will be between one and four times (both inclusive)the refrigerating machine oil 60 in terms of weight ratio, therefrigeration cycle apparatus 10 can be controlled stably, making itpossible to achieve a sufficient COP improvement effect andhigh-pressure reduction effect.

Note that the composition of the mixed refrigerant(HFO-1123:R32:HFO-1234yf=40:40:20) in a state before the mixedrefrigerant is enclosed in the refrigerant circuits is strictlyexemplary. However, if the ratio of HFO-1234yf increases too much, thereis concern that an increased pressure loss may degrade the performanceof the refrigeration cycle apparatus 10. Thus, preferably the ratio ofHFO-1234yf is 50 wt % or less.

Besides, the dissolved amounts of refrigerants shown in FIGS. 4 and 5are also strictly exemplary. Under operating conditions in which the dewpoint temperature is 40 degrees C. and the temperature of therefrigerating machine oil 60 accumulated in the compressor 12 is 60degrees C., by adjusting the refrigerating machine oil 60 such that thedissolved amount of HFO-1234yf will be 30 parts or above by weight, andthat the dissolved amount of R32 will be 10 parts or more by weight lessthan the dissolved amount of HFO-1234yf, the effects described above canbe achieved sufficiently.

An embodiment of the present invention has been described above, but theembodiment may be implemented partially. For example, one or some of theelements denoted by symbols in the drawings may be omitted or replacedby other elements. Note that the present invention is not limited to theabove embodiment, and various changes may be made as required.

Reference Signs List 10 refrigeration cycle apparatus 11a, 11brefrigerant circuit 12 compressor 13 four-way valve 14 outdoor heatexchanger 15 expansion valve 16 indoor heat exchanger 17 controller 20airtight container 21 suction pipe 22 discharge pipe 23 suction muffler24 power supply terminal 30 compression element 31 cylinder 32 rollingpiston 33 main bearing 34 secondary bearing 35 discharge muffler 40electrically-operated element 41 stator 42 rotor 43 stator core 44stator winding 45 lead wire 46 rotor core 48 insulating member 50 shaft51 eccentric shaft portion 52 main shaft portion 53 secondary shaftportion 60 refrigerating machine oil

The invention claimed is:
 1. A refrigeration cycle apparatus comprising:a refrigerant circuit in which a high-pressure shell compressor, acondenser, an expansion mechanism and an evaporator are connected; amixed refrigerant circulating through the refrigerant circuit andcontaining 1,1,2-trifluoroethylene, difluoromethane and2,3,3,3-tetrafluoropropene mixed with each other, wherein, in a stateprior to introduction of the mixed refrigerant into the refrigerantcircuit, a percentage by weight of the 1,1,2-trifluoroethylene iscontained in the mixed refrigerant in an amount less than 50 wt %, and apercentage by weight of the difluoromethane is contained in an amount ofat least 0.7 times but not more than two times the percentage by weightof the 1,1,2-trifluoroethylene in terms of weight ratio; and arefrigerating machine oil is enclosed in the refrigerant circuittogether with the mixed refrigerant in an amount equal to and up to fourtimes the weight of the mixed refrigerant in terms of weight ratio, therefrigerating machine oil being a solvent for the mixed refrigerant witha portion of each of the difluoromethane, the 1,1,2-trifluoroethyleneand the 2,3,3,3-tetrafluoropropene being dissolved in the refrigeratingmachine oil enclosed in the refrigerant circuit, wherein therefrigerating machine oil satisfies a relationship that thedifluoromethane has a smaller solubility in the refrigerating machineoil compared to solubilities of the 1,1,2-trifluoroethylene and the2,3,3,3-tetrafluoropropene in the refrigerating machine oil, and therefrigerating machine oil reduces the amount of the1,1,2-trifluoroethylene contained in the mixed refrigerant enclosed inthe refrigerant circuit for inhibiting a disproportionation reaction ofthe 1,1,2-trifluoroethylene during operation of the refrigeration cycleapparatus.
 2. The refrigeration cycle apparatus of claim 1, wherein therefrigerating machine oil satisfies another relationship that the2,3,3,3-tetrafluoropropene is more soluble in the refrigerating machineoil than the 1,1,2-trifluoroethylene.
 3. The refrigeration cycleapparatus of claim 1, wherein under operating conditions in which a dewpoint temperature is 40 degrees C. and a temperature of therefrigerating machine oil accumulated in the high-pressure shellcompressor is 60 degrees C.: 30 parts by weight or more of the2,3,3,3-tetrafluoropropene is dissolved in the refrigerating machine oilper 100 parts by weight of the refrigerating machine oil; and an amountof the difluoromethane dissolved in the refrigerating machine oil per100 parts by weight of the refrigerating machine oil is less than thedissolved amount of the 2,3,3,3-tetrafluoropropene by 10 parts by weightor more.
 4. The refrigeration cycle apparatus of claim 1, wherein therefrigerating machine oil comprises at least one of polyol ester,polyvinyl ether, and polyalkylene glycol.
 5. The refrigeration cycleapparatus of claim 1, wherein during operation of the refrigerationcycle apparatus, the refrigerating machine oil prevents an increase in aweight amount of the 1,1,2-trifluoroethylene dissolved in the mixedrefrigerant enclosed in the refrigeration circuit compared to the weightamount of the 1,1,2-trifluoroethylene in the mixed refrigerant in thestate prior to introduction into the refrigerant circuit for inhibitingthe disproportionation reaction of the 1,1,2-trifluoroethylene.
 6. Therefrigeration cycle apparatus of claim 1, wherein during operation ofthe refrigeration cycle apparatus, the refrigerating machine oildissolves different amounts of the difluoromethane,1,1,2-trifluoroethylene and the 2,3,3,3-tetrafluoropropene, resulting inthe mixed refrigerant enclosed in the refrigeration circuit having aweight amount of 2,3,3,3-tetrafluoropropene greater than a weight amountof 1,1,2-trifluoroethylene and a weight amount of1,1,2-trifluoroethylene being greater than the weight amount ofdifluoromethane.
 7. The refrigeration cycle apparatus of claim 1,wherein the weight of the refrigerating machine oil is greater than theweight of the mixed refrigerant and up to four times the weight of themixed refrigerant in terms of weight ratio.
 8. The refrigeration cycleapparatus of claim 1, wherein the refrigerating machine oil comprises atleast one of a polyol ester, a polyvinyl ether, and a polyalkyleneglycol, and the polyol ester is a product of esterification of a fattyacid and polyhydric alcohol, and the solubility of each refrigerant inthe polyol ester is adjusted by varying a carbon number of the fattyacid, selecting a molecular structure of the fatty acid from abranch-chain fatty acid and an unbranched (straight-chain) fatty acid,varying a carbon number of the polyhydric alcohol, and selecting amolecular structure of the polyhydric alcohol from a branched-chainpolyhydric alcohol and an unbranched (straight-chain) polyhydricalcohol, the polyvinyl ether is a compound in which alkyl groups arelinked to side chains of a straight-chain hydrocarbon via etherlinkages, and the solubility of each refrigerant in the polyvinyl etheris adjusted by varying components of the alkyl group linked to the sidechains via ether linkages, and polyalkylene glycol is a compound inwhich a propylene oxide and ethylene oxide are linked together in chainsvia ether linkages, and the solubility of each refrigerant in thepolyethylene glycol is adjusted by varying a ratio between the propyleneoxide and ethylene oxide.
 9. A refrigeration cycle apparatus comprising:a refrigerant circuit in which a high-pressure shell compressor, acondenser, an expansion mechanism and an evaporator are connected; amixed refrigerant circulating through the refrigerant circuit andcontaining 1,1,2-trifluoroethylene, difluoromethane and2,3,3,3-tetrafluoropropene mixed with each other; and a refrigeratingmachine oil is enclosed in within the refrigerant circuit combined withthe mixed refrigerant, the mixed refrigerant being in contact with therefrigerating machine oil while circulating through the refrigerantcircuit, an amount of the refrigerating machine oil being equal to aweight of the mixed refrigerant and up to four times the weight of themixed refrigerant in terms of weight ratio, wherein, in an unenclosedstate of the mixed refrigerant which is prior to introducing the mixedrefrigerant into the refrigerant circuit and combining the mixedrefrigerant with our refrigerating machine oil, the1,1,2-trifluoroethylene is contained in the mixed refrigerant in anamount less than 50 wt %, and the difluoromethane is contained in themixed refrigerant in an amount of at least 0.7 times but not more thantwo times an amount of the 1,1,2-trifluoroethylene in terms of weightratio of the 1,1,2-trifluoroethylene to the difluoromethane, and aweight ratio of the difluoromethane to a total weight of the mixedrefrigerant being based on the amount of 1,1,2-trifluoroethylene and theweight ratio of the 1,1,2-trifluoroethylene to the difluoromethane, andwherein, in an enclosed state of the mixed refrigerant where the mixedrefrigerant is combined with the refrigerating machine oil and enclosedin the refrigerant circuit, the weight ratio of the difluoromethane tothe total weight of the mixed refrigerant is larger than the weightratio of the difluoromethane to the total weight of the mixedrefrigerant in the unenclosed state of the mixed refrigerant.
 10. Therefrigeration cycle apparatus of claim 9, wherein the refrigeratingmachine oil satisfies a relationship that the 2,3,3,3-tetrafluoropropeneis more soluble in the refrigerating machine oil than the1,1,2-trifluoroethylene.
 11. The refrigeration cycle apparatus of claim9, wherein under operating conditions in which a dew point temperatureis 40 degrees C. and a temperature of the refrigerating machine oilaccumulated in the high-pressure shell compressor is 60 degrees C.: 30parts by weight or more of the 2,3,3,3-tetrafluoropropene is dissolvedin the refrigerating machine oil per 100 parts by weight of therefrigerating machine oil; and an amount of the difluoromethanedissolved in the refrigerating machine oil per 100 parts by weight ofthe refrigerating machine oil is less than the dissolved amount of the2,3,3,3-tetrafluoropropene by 10 parts by weight or more.
 12. Therefrigeration cycle apparatus of claim 9, wherein the refrigeratingmachine oil comprises at least one of polyol ester, polyvinyl ether, andpolyalkylene glycol.
 13. The refrigeration cycle apparatus of claim 9,wherein the refrigerating machine oil has a molecular structure in whichan increased weight amount of the 1,1,2-trifluoroethylene is dissolvedinto the refrigerating machine oil relative to dissolved amounts ofdifluoromethane and the 1,1,2-trifluoroethylene for inhibiting thedisproportionation reaction of the 1,1,2-trifluoroethylene.
 14. Therefrigeration cycle apparatus of claim 9, wherein the refrigeratingmachine oil has a molecular structure so that different amounts of thedifluoromethane, 1,1,2-trifluoroethylene and the2,3,3,3-tetrafluoropropene dissolve in the mixed refrigerant whichresults in the weight amount of 2,3,3,3-tetrafluoropropene being greaterthan the weight amount of 1,1,2-trifluoroethylene and the weight amountof 1,1,2-trifluoroethylene being greater than the weight amount ofdifluoromethane which relationship inhibits the disproportionationreaction of the 1,1,2-trifluoroethylene.
 15. The refrigeration cycleapparatus of claim 9, wherein the weight of the refrigerating machineoil is greater than the weight of the mixed refrigerant and up to fourtimes the weight of the mixed refrigerant in terms of weight ratio. 16.The refrigeration cycle apparatus of claim 9, wherein the refrigeratingmachine oil comprises at least one of a polyol ester, a polyvinyl ether,and a polyalkylene glycol, and the polyol ester is a product ofesterification of a fatty acid and polyhydric alcohol, and thesolubility of each refrigerant in the polyol ester is adjusted byvarying a carbon number of the fatty acid, selecting a molecularstructure of the fatty acid from a branch-chain fatty acid and anunbranched (straight-chain) fatty acid, varying a carbon number of thepolyhydric alcohol, and selecting a molecular structure of thepolyhydric alcohol from a branched-chain polyhydric alcohol and anunbranched (straight-chain) polyhydric alcohol, the polyvinyl ether is acompound in which alkyl groups are linked to side chains of astraight-chain hydrocarbon via ether linkages, and the solubility ofeach refrigerant in the polyvinyl ether is adjusted by varyingcomponents of the alkyl group linked to the side chains via etherlinkages, and polyalkylene glycol is a compound in which a propyleneoxide and ethylene oxide are linked together in chains via etherlinkages, and the solubility of each refrigerant in the polyethyleneglycol is adjusted by varying a ratio between the propylene oxide andethylene oxide.